In Emacs on Ubuntu Raring.. I have SBCL loaded in Emacs because i use it all the time. I type (ql:quickload "ieee-floats") to load my first library on a freshly installed ACL in emacs after typing M-- M-x slime to load ACL and get this error:

While searching for system "ieee-floats": #P"/home/b/quicklisp/dists/quicklisp/software/c2ffi/README" evaluated to #P"/home/b/quicklisp/dists/quicklisp/software/c2ffi/README" which is not a directory.

so acl is just looking at first file and stopping. Also in the asdf:central-registry in ACL it list all the files in the root directory as well as the folders but in SBCL it just lists all the root folders in quicklisp/dist/software and SBCL works for installing quicklisp libraries i/e